Steel and articles made therefrom



?atented Oct. 10, 1933 1,9295% STEEL ARTICLES MADE THEREFRQIVI Augustus B. to Electro tion of West Virginia Kinzel, Beechhurst, N. Y., assignor Metallurgical ompany, a corpora- No Drawing. Application June 9, 1931 Serial No.

3 Claims. (or. 75 -1) 7 The invention comprises a novel steel composition, and certain articles for which the composition is especially adapted.

The essential constituents-oi invention are iron, chromium, manganese an silicon. It is of course exclude carbon when manufacturing the steel on a commercial scale, but the carbon content should not exceed about 0.2%. Where the highest degree of ductility is required, the carbon content should not exceed 0.10%. Steels in which the carbon content is the lowest which it is possible to reach in commercial .operations are useful for many purposes.

The respective lower and upper limits for chromium are approximately 0.2% and 2.5%, for manganese 0.6% and 2.5%, and for silicon 0.2% and 2.5%. In a preferred class of compositions, the chromium does not exceed 0.75%.

The hereindescribed steels have the peculiarity that their strength seems abnormally high when they are compared with other alloy steels of similar carbon content. At the same time they display the high ductility of low'carbon compositions. If a steel according to the invention is modified by increasing its carbon content, say to 0.35%, and it is then compared with one of the common alloy stee such as chromevanadium steel having a similar carbon content, the physical propertiesof the two steels will be found not to differ markedly. Then, if the carbon content of the two steels under comparison is gradually diminished, a conspicuous. divergence in the physical properties begins at about 0.2% carbon. Below that value the chromevanadium steel continues to increase in ductility but rapidly loses its strength. The steel of the invention also becomes highly ductile but its strength falls oil very much more slowly than in the case-of the chrome-vanadium steel. This leads to the inference that the chrome-vanadium steel owesits strength in large part to a joint action of carbon and the alloying constituents, both being indispensible, whereas in the steel of the invention there is an important strengthening effect which is not dependent on the presence oi carbon.

The hereindescribed steel is particularly useful as a material for articles which must have a very high degree of ductility, in that i ofiers a means of giving such articles much greater strength than they usually possess. Examples of articles in which extreme ductility is required are stay bolts, and other types of rivets. In or- 55 do: to develop the desired ductility it is now custhe steel of the inches.

tomary to use very low carbon steel for such articles. A steel containing 0.25% chromium, 1.1% manganese, 0.7% silicon, and 0.05% carbon has an ultimate strength as rolled of 70,000

d lbs. per sq. in., with an elongation of 33% in 8 inches. In ductility this steel is comparable with the softest stay bolt material in use before my invention, but such material has an ultimate strength of only about 45,000 lbs. per

sq. in.

The steels of my invention may also be used for. making articles like boiler plates, which do not require qu'te as much ductility as is needed in rivets. For such articles the carbon is preferably in the upper part of its range, that is, in the vicinity of 0.2%. A steel containing 0.5% chromium, 1.1% manganese, 0.75% silicon, and 0.2% carbon has an ultimate strength of 90,000 lbs. per sq. in. as rolled, with 20% elongation in 8 This elongation is of the same order as that of the usual 0.18%-0.20% carbon boiler plate, whereas the ultimate strength of the latter is only about 55,000 lbs. per' sq. in.

The hereindescribed steels can be heat-treated in anyusual way, as by quenching with or without drawing, but they also develop desirable qualities, including a high degree of strength, when merely air-cooled, [as will be apparent from the examples cited above.

1. A steel consisting substantially of iron, chromium, manganese, carbon, and silicon, the chromium content be g between 0.2% and 0.75%, the manganese between 0.6% and 2.5%, the silicon between 0.2% and 2.5%, and the carbon content below 0.1%.

2. A steel consisting of about 0.5% chromium, about 1.1% manganese, about 0.75% silicon and about 0.05% carbon the balance being substantially all iron.

3. A rivet composed of a steel consisting substanti'ally of iron, chromium, manganese, carbon, and silicon, the chromium content being between 0.2% and 0.75%, the manganese between 0.6% and 2.5%, the s'licon between 0.2% 100 ands2.5%,land the carbon content below 0.1%.

. AUGUSTUS B. KINZEL. 

